Wednesday, February 29, 2012

Unfortunately, many of the areas that were affected by damaging thunderstorms today will be under the gun again on Friday, with a widespread severe thunderstorm and tornado outbreak possible once again.

The above image shows the latest severe weather outlook for Friday, from the Storm Prediction Center. Severe weather is likely within and near the yellow shaded areas on the image.

The above video was taken yesterday evening, February 28, 2012, by an unidentified storm chaser near Stapleton, Nebraska. It shows the first tornado ever to be documented in Nebraska during the month of February. Records have been kept back as far as 1880 (near as I can tell). So this was definitely a major event.

Here is another, more extensive, video taken by "Colorado Storm Chaser":

The good thing about tornadoes like this one is that they take place in a very rural area. No people or property were impacted as far as I can tell.

Nebraska is a beautiful place. I have chased many a storm there, and the tornadoes are always as picturesque as can be...and often track through the farmland while not causing harm to anyone around.

I'll never forget chasing a storm near Broken Bow, Nebraska during the summer of 1990. We were shooting pictures of a tornado in a rural area, while parked in a church parking lot (the church was by no means in danger or we would have gone in and warned the folks inside - the parking lot was full, the tornado was North of the church and moving to the East). Someone came out of the church and said "are you guys lookin' for the weddin'..." I didn't say a word to the gentleman...I just simply pointed to the tornado to the North... He shouted a word that was probably not appropriate for church, and ran back inside...

A band of strong to severe thunderstorms currently extends from southeastern Kentucky across the middle third of Tennessee, and are developing Southwest across northern Mississippi and northeast Louisiana:

At this time, the highest threat of severe weather, including damaging winds and tornadoes, is located within an area extending from northeast Mississippi across middle Tennessee and into southeastern Kentucky, generally within the area outlined in solid red on the image below (along and to the East of the thunderstorm line within that region):

Folks all across the severe weather watch areas, and particularly along and ahead of the line of storms from northern Mississippi (and northwest Alabama) into middle Tennessee and southeast Kentucky should remain on a high state of alert this afternoon and evening. Listen to local media or another trusted source for the latest weather information and possible warnings. Take a few moments to review severe weather safety and preparedness tips, that way you're ready to take action when threatening weather approaches your area. This includes identifying the best sheltering option and having a plan in place to get there quickly.

The above Tornado Watch was just issued for much of central and eastern Ohio and portions of West Virginia. It is valid until 9pm EST. This tornado watch includes the cities of Columbus, Cleveland, Canton-Akron, Zanesville, Parkersburg, Charleston, Huntington and Beckley.

Strong to severe storms are moving up into this region from the Southwest, and additional development will take place across the region during the afternoon hours as well.

Large hail, damaging winds and tornadoes are all possible with the activity this afternoon and evening.

If you live across this region, be sure to remain alert this afternoon and evening. Listen to local media or another trusted source for the latest weather information and possible warnings. Take a few moments to review severe weather safety and preparedness tips, that way you're ready to take action when threatening weather approaches your area. This includes identifying the best sheltering option and having a plan in place to get there quickly.

Strong to severe thunderstorms continue to move and develop toward the East across Kentucky and northwestern Tennessee at this hour. A newtornado watch was just issued for this region, and is valid until 8pm CST this evening:

The activity is likely to undergo a period of intensification and reorganization during the afternoon, with the threat of severe weather, including tornadoes, expected to remain quite high across the red and black hatched areas on the image below, where a strong tornado or two are possible:

Folks living across this region should remain alert this afternoon and evening. Listen to local media or another trusted source for the latest weather information and possible warnings. Take a few moments to review severe weather safety and preparedness tips, that way you're ready to take action when threatening weather approaches your area. This includes identifying the best sheltering option and having a plan in place to get there quickly.

A band of strong to severe thunderstorms continues to press Eastward this morning, currently stretching from northwest Kentucky back into northcentral Arkansas. Large hail and damaging wind gusts have continued to be reported with the line, along with a few tornadoes overnight.

Significant wind and/or tornado damage took place overnight in the Branson, MO and Harrisburg, IL areas. I'll have more details on this in later post(s)...

Tornado Watches are currently in effect for the red outlined areas on the image below:

The threat of severe weather will continue to progress to the East during the day today. The latest severe weather outlook from the Storm Prediction Center (SPC) is shown below. Severe thunderstorms are possible today anywhere within the yellow shaded areas on the image, with the greatest threat within the red shaded areas:

Large hail, damaging winds and some tornadoes are all possible with the severe storms today. The highest tornado threat is expected to take place within the red shaded and black hatched areas on the image below, which includes the cities of Bowling Green, KY and Nashville, Chattanooga, and Jackson, TN:

Within this region, a strong and/or long tracked tornado is possible. A significant threat of damaging winds will also exist across the region, with the highest risk within the red and lavender shaded areas on the image below:

Folks living across the above mentioned areas should remain alert today. Listen to local media or another trusted source for the latest weather information and possible warnings. If you are within the threat area(s) but still ahead of the storms at this time, take a few moments to review severe weather safety and preparedness tips, that way you're ready to take action when threatening weather approaches your area. This includes identifying the best sheltering option and having a plan in place to get there quickly.

Tuesday, February 28, 2012

The above radar mosaic image shows a line of strong to severe thunderstorms extending from West of Omaha to near Ponca City Oklahoma. This activity is moving toward the East/Northeast at up to 55 mph.

A Tornado Watch continues until 1am CST for eastern Kansas and northcentral and northeastern Oklahoma:

This watch includes the Topeka, Manhattan, Lawrence, Emporia, Chanute, Stillwater and Tulsa areas.

Although an isolated tornado cannot be ruled out... large hail and damaging thunderstorm wind gusts are the primary severe weather threats across this region.

Based on their present location and movement, the thunderstorm activity can be expected to reach the Kansas City Metro area between 10:30pm and 11:30pm CST, and the Tulsa Metro area after 11pm and toward Midnight CST.

Once passing through these areas, the severe weather threat will continue into the overnight and pre-dawn hours Wednesday into southwestern Missouri and much of central and northern Arkansas.

Severe weather can be especially dangerous at night. If you live in these areas make sure that you have a way to receive weather warnings overnight, such as a NOAA Weather Radio with a battery back-up, a smartphone application, text or phone alert service, etc. Be sure to identify your potential sheltering location(s) ahead of time, that way you can quickly move to that area if necessary.

Please...be sure that you never count on outdoor tornado warning sirens to warn you of a threat when inside. As the name implies, they were not designed to provide indoor warnings, and you may not be able to hear them depending on your location relative to the siren, the storm's location, and other factors.

The above Tornado Watch was just issued by the Storm Prediction Center (SPC)in Norman, OK. It is valid until 1am CST and includes the cities of Tulsa, Ponca City, Wichita, Emporia, Topeka and Chanute.

Large hail and strong, possibly damaging wind gusts are the primary threats, however isolated tornadoes are also possible.

Strong to severe thunderstorms are forming a line near the Western edge of the watch area, and will continue to move and develop toward the East/Northeast during the late evening and early overnight hours.

If you live in this region, please listen to NOAA Weather Radio or another trusted source for later statements and possible warnings. Have a sheltering plan in mind and be prepared to go there immediately if threatening weather approaches your area...

The above Tornado Watch was just issued by theStorm Prediction Center (SPC)in Norman, OK. It is valid until 11pm CST and includes the cities of Wichita, Russell, Great Bend, Salina and Hutchinson.

Thunderstorms are developing along and ahead of a surface cold front and dryline across the western part of central Kansas. This trend will continue as the activity moves and develops toward the East/Northeast this evening.

Large hail and strong, possibly damaging wind gusts are the primary threats, however isolated tornadoes are also possible.

If you live in this region, please listen to NOAA Weather Radio or another trusted source for later statements and possible warnings. Have a sheltering plan in mind and be prepared to go there immediately if threatening weather approaches your area...

The above Tornado Watch was just issued by the Storm Prediction Center (SPC) in Norman, OK. It is valid until 9pm CST and includes the cities of Concordia, Grand Island, Hastings and Lincoln.

Thunderstorms are developing along and ahead of a surface cold front and dryline across southwest and southcentral Nebraska into northcentral Kansas. This trend will continue as the activity moves East/Northeast this evening.

Large hail and strong, possibly damaging wind gusts are the primary threats, however isolated tornadoes are also possible.

If you live in this region, please listen to NOAA Weather Radio or another trusted source for later statements and possible warnings. Have a sheltering plan in mind and be prepared to go there immediately if threatening weather approaches your area...

At midday today, a powerful storm system in the middle and upper atmosphere was swirling about over the central and northern Rockies. This system is forecast to lift out to the East/Northeast across the adjacent Plains tonight.

At the surface, an area of low pressure was organizing over the central Rockies. This area of low pressure will move East into the Plains, reaching central Nebraska by 6pm CST and moving into southern Minnesota by dawn on Wednesday. A cold front and dryline will trail the surface low to the South across the Plains.

Thunderstorms are forecast to develop along and ahead of these features this evening and tonight, with an attendant risk of severe weather. The latest outlook from the Storm Prediction Center (SPC) in Norman, OK is calling for severe thunderstorm development within the yellow shaded areas on the image below:

The way I currently see this shaping up, there will be 3 distinctive rounds of severe weather potential this evening and/or tonight. Each will carry specific threats and will likely take place during relatively specific periods of time:

First, I expect the initial round of potentially severe thunderstorm activity to develop by mid-evening over southwestern and/or southcentral Nebraska into northcentral Kansas. This would include the cities of Grand Island, Hastings, Russell, Hays and Concordia:

Hail to severe limits (i.e., 1 inch in diameter or larger) will be the primary threat with this activity, which is likely to move and/or develop East/Northeast toward the Missouri River by Midnight. An isolated tornado or two cannot be completely ruled out.

A second area of severe weather is likely to develop Southward along the dryline and/or cold front across eastern Kansas, southeast Nebraska and into eastern Oklahoma later this evening. This would most likely take place after dark, and even more likely after 9pm CST:

Large hail, damaging wind gusts and isolated tornadoes will be possible with this activity. This threat includes the cities of Omaha, Kansas City, Emporia, Ponca City, Enid, Tulsa and Chanute.

Once developed, this activity will progress toward the Eastern edge of the outlook area by Midnight, and pressing further toward the East during the overnight hours, as indicated on this image, which identifies the primary threat area from Midnight through 6am CST Wednesday:

Note that the northern portion of this area will likely see the threat diminish by 3am CST, while the threat will continue further South across southwest Missouri and northwestern through northcentral Arkansas.

Late in the night and toward dawn, I would expect the above activity to congeal into a larger complex of thunderstorms, with large hail and damaging winds the primary threats, which will shift toward the Mississippi River toward dawn on Wednesday:

As you can see, the potential exists for a significant portion of the severe weather threat to take place either after dark and/or after Midnight tonight. If you live in these areas, please make sure that you are prepared to act quickly if threatening weather approaches during the late evening or overnight hours.

Please...be sure that you never count on outdoor tornado warning sirens to warn you of a threat when inside. As the name implies, they were not designed to provide indoor warnings, and you may not be able to hear them depending on your location relative to the siren, the storm's location, and other factors.

I'll be posting updates on the latest trends this evening, so check back for any significant updates...

Above is the latest severe weather outlook for today and tonight from the Storm Prediction Center (SPC) in Norman, OK. Severe thunderstorms are forecast within the yellow shaded areas on the above image.

A very strong middle and upper-level storm system and associated surface front will move across the outlook area, generally from West to East, later today and tonight.

The initial threat of severe storms will take place along the front from southeastern Nebraska into northcentral Kansas late this afternoon, and continue Eastward into southwest Iowa and northwest Missouri this evening. Large hail and damaging wind gusts will be the primary severe weather threats in these areas, although an isolated tornado cannot be completely ruled out.

Isolated to scattered severe storms may form Southward along the cold front and/or dryline into southcentral Kansas and central or southwestern Oklahoma by early to mid-evening. Coverage is not expected to be widespread in this region at this time, however any storm that does form will be capable of producing large hail, damaging winds and isolated tornadoes.

A more widespread and significant threat of severe weather is forecast to develop late this evening and into the overnight hours tonight. This will primarily take place from eastern Oklahoma into western Arkansas, with the activity then expanding toward the East as it approaches the Mississippi River toward the pre-dawn hours of Wednesday. Large hail, damaging winds and tornadoes will all be possible with this activity.

The greatest threat of tornado development will be within and near the yellow shaded areas on the following image:

...with the highest threat of damaging winds within the red shaded area on this image:

The potential exists for a significant round of severe weather during the overnight hours, mainly from the Oklahoma/Arkansas border Eastward to the Mississippi River. This includes the cities of Ft. Smith, Little Rock and Memphis.

Folks living in this region should review severe weather safety and preparedness tips today and have a plan of action in place prior to the arrival of this threat. Be sure that you have a way to receive severe weather warnings at night, such as a NOAA Weather Radio, smartphone application, text alert, etc.

Watch for an update later this afternoon as the situation continues to unfold.

Monday, February 27, 2012

The same storm system that will bring a threat of severe weather to the central and southern Plains into the Mississippi River Valley tomorrow afternoon and night will bring widespread snow, some heavy, to the northern Plains at about the same time.

The above image shows current Winter Weather Watches, Warnings and Advisories across the region. Winter Storm Warnings are in effect for the pink shaded areas (including the Minneapolis-St. Paul area), while a Blizzard Warning is in effect for the orange shaded areas over the Dakotas and west-central Minnesota.

Heavy snow will fall across the northern and central Rockies tonight and the first half of Tuesday:

Probability of 8+ Inches of Snow thru 6pm CST Tuesday

...and then spread out into the adjacent Plains by Tuesday evening and night:

Probability of 8+ Inches of Snow 6pm CST Tuesday-6pm Wednesday

This winter has been relatively quiet across much of this region, snowfall wise. If you live across the warning areas, make sure that you're ready to stay indoors until the worst of the weather passes your area. Take the time now to purchase needed supplies and stock your severe weather emergency kit.

A very strong middle and upper-level storm system will move out over the Central Plains on Tuesday afternoon and evening, along with a strong area of low pressure and frontal boundary at the surface. While there is no question that the dynamics of these systems are quite strong (which would normally lead to widespread severe weather), there are still many questions about just how extensive of an event this will turn out to be.

The above image is the latest severe weather outlook for Tuesday and Tuesday Night, from the Storm Prediction Center (SPC) in Norman, OK. Severe thunderstorms are possible within and near the yellow shaded areas on the image. Large hail, damaging wind gusts and a few tornadoes are all possible with severe storms across this region.

Thunderstorms are forecast to develop along and ahead of the surface cold front across the Kansas/Nebraska outlook area by mid-afternoon and continue Eastward during the evening hours. Hail and damaging wind gusts are the primary threats, however an isolated tornado or two cannot be ruled out in this region.

Further South, the situation is less clear-cut. Low-level moisture will begin flowing rapidly Northward into the Oklahoma and Arkansas risk area tonight. This will lead to widespread cloudiness, as well as light precipitation breaking out during the day Tuesday. The main question is how much of an effect the cloudiness and rain will have on the atmosphere's ability to become unstable enough to support a severe weather threat.

At this time, I would expect thunderstorms to develop along the cold front and or dryline near the Western edge of the severe weather outlook area in Oklahoma by mid to late evening Tuesday, with the threat then shifting Eastward into Arkansas and the middle to lower Mississippi Valley region after Midnight and into the pre-dawn hours Wednesday.

The wind profile across this region will be favorable for some storms to rotate and produce tornadoes. Damaging wind gusts and large hail are also possible with severe storms in this region.

Folks living across the above mentioned areas should remain alert on Tuesday and Tuesday Night. Listen to local media or another trusted source for the latest weather information and possible warnings. I would strongly suggest that you take the time now to review severe weather safety and preparedness tips, that way you're ready to take action if threatening weather approaches your area.

Sunday, February 26, 2012

At midday (approximately 1:07 PM EST) on February 24, 2012, a tornado touched down near Wagener, SC, along the Lexington/Aiken County lines. This tornado had a maximum path width of 100 yards, and was on the ground for approximately 8 miles before lifting near the intersection of Greens Bridge and Charles Town roads. The National Weather Service (NWS) storm survey rated this tornado EF-2 intensity, with maximum sustained winds estimated at 130 mph.

The series of photos below show some of the damage as noted by the NWS survey team:

Radar imagery from the Columbia, SC area radar showed widespread, heavy precipitation at the time and location of the tornado touchdown (yellow circled area on the image below), which likely means the circulation was rain wrapped and may not have been visible to those in its path:

When examining the velocity data, remember that green colors indicate wind blowing toward the radar, while the red shadings indicate winds blowing away from the radar. The radar is located just off of the upper-right hand corner of the image.

This was the strongest of 9 tornadoes that were reported on February 24th. The other tornadoes were rated EF-0 or EF-1 intensity(click to enlarge):

With the spring severe weather season fast approaching, I thought it would be a good time to review some related material over the coming days and weeks. This post on the Enhanced Fujita Scale of Tornado Intensity was originally made in August of 2010:

The Enhanced Fujita (EF) Scale rates the strength of tornadoes in the U.S. based on the character and intensity of damage that they cause to existing structures.

In 1971, tornado pioneer Ted Fujita developed the F-Scale (or Fujita Scale) of tornado intensity. While the new EF-Scale operates on the same basic premise as the original F-Scale, it was revised to better reflect the results of tornado damage surveys. The EF Scale attempts to align tornado wind speed estimates more closely with observed structural damage on the ground. The EF-Scale was officially launched for use in February of 2007.

The EF-Scale chart below was adopted from the Wikipedia article on the subject, found here.